Inflatable underground structure liner

ABSTRACT

An underground structure liner based upon an inflatable liner structure. An acid resistant layer is the innermost layer of an inflatable liner, and the liner is coated with epoxy resin on its outermost surface, the surface which contacts the existing walls of the underground structure. The outermost coated surface of the liner is constructed with a fibrous fleece layer for better retention of the epoxy and better adhesion of the epoxy to the walls of the underground structure. An added feature of the liner is a structure which also seals the liner to pipes entering the underground structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/071,433 filed Feb. 8, 2002, now U.S. Pat. No. 6,540,438, which is acontinuation of U.S. application Ser. No. 09/604,839, filed Jun. 27,2000, now abandoned. The disclosures of each of the foregoingapplications are hereby incorporated herein by reference, in theirentirety.

BACKGROUND OF THE INVENTION

The invention deals generally with underground structures such asmanholes, utility vaults, and pump stations, and more specifically witha method and apparatus to attach an impermeable continuous liner toprevent corrosion by the effects of sewer gas and to prevent fluidleaking into the underground structure.

Underground structures such as manholes serve to connect pipes, transfersewage, and provide maintenance access. When they permit ground water toleak in, they contribute to unnecessary sewage treatment costs or damagethe sewer lines or other utility services which pass through theunderground structures. Furthermore, microorganisms that consume sewergas form sulfuric acid, and this acid dissolves the undergroundstructure walls which may lead to deterioration, collapse, serviceinterruption, or accidents.

This deterioration is caused mainly because of the nature of theoriginal structure. Underground structures such as manholes areessentially chambers in the ground, sometimes large vertical shafts,which extend to the depth at which sewer pipes or utility services arelocated. The older chambers are usually built of bricks or cementblocks, with the bricks or blocks assembled with mortar joints. Thesematerials, and particularly the joints, deteriorate with time because ofsuch factors as traffic loads, ground water, soil pressure, and septicgases. Even cast concrete underground structures can be damaged by suchcauses, particularly from the acids septic gases create and which attackmost materials.

Once an underground structure is damaged and leaking, it is verydifficult to repair it so that it is watertight and gas tight, andcompletely rebuilding it is costly and time consuming because itrequires excavating all around the underground structure.

Several patents have been issued on a newer approach to repairingunderground structure chambers. The technique involves attaching a linerto the inside wall surface of the underground structure chamber. Asdescribed in U.S. Pat. Nos. 5,490,744 and 5,265,981 by McNeil, the lineris typically a long fiberglass bag covered with an epoxy resin. This bagis lowered into the underground chamber, inflated by the use of aremovable interior inflatable bladder until it presses against theinside walls of the underground chamber, and the resin is cured inplace. The result is the formation of a new chamber which conforms tothe original underground structure regardless of whether the chamber isa straight cylinder or it has an irregular shape. However, this type ofadditional internal chamber still has problems.

The structure of the McNeil liners, which have fiberglass and resins onthe exposed surfaces, are themselves attacked by septic gases. Thiscauses erosion of the exposed fiberglass layers which deteriorate overtime and ultimately weaken the rehabilitation structure. Furthermore, atliner termination points such as junctions where the liner is joined topipes and flow channels, gas infiltration leads to corrosion of theunderground structure walls and destruction of the liner bond.

It would be very beneficial to have a underground structure liner whichwas chemically stable, allows gas-tight joints with pipe lining, andprevents fluid leakage into the underground chamber.

SUMMARY OF THE INVENTION

The present invention solves the problems with crumbling of fiberglassepoxy layers that are exposed to sewer gas and of joint adhesion withpipe linings by constructing the liner in a different fashion. The linerof the present invention includes two essential layers. The first layeris an acid resistant layer which is the innermost layer, the layerexposed to the environment of the underground structure. The secondlayer is located on the outside and is the layer in contact with thewall of the underground structure. This layer is a fleece layer, acontinuous layer of fibers protruding from the acid resistant layer. Thefleece layer is integrated into the acid resistant material and servesto capture and retain the epoxy resin applied to the liner. Furthermore,the fibers of the fleece layer function as multiple anchors as theycontact the wall of the underground structure and form a continuouslayer which conforms to irregularities and crevices in the undergroundstructure wall surface Reinforcing material can also be added to thefleece layer. Typically this reinforcing material is a cloth layer whichis also saturated with resin, and it can be added to the outside of thefleece layer. However, the reinforcing material can also be integratedinto the epoxy resin by applying a mixture of epoxy resin and fibersdirectly onto the fleece layer.

In the preferred embodiment the material of the acid resistant layer ispolyvinyl chloride (PVC), the fleece layer is polyester, and the clothlayer is fiberglass. The thicknesses of the layers can be adjusted forthe specific application to yield, for instance, greater strength oracid resistance.

Several methods of applying the epoxy resin are available. A two partresin can be applied to the fleece layer or to the fiberglass layer atthe installation site just before insertion into the undergroundstructure. A delayed reaction epoxy can also be applied to the linerbefore it arrives at the installation site, in which case the epoxy iscured by subjecting the assembly to elevated temperature or to someother activating agent such as light or other radiation.

The present invention also affords a means to create a superior sealbetween the liner installed within the underground structure and thepipes entering into the underground structure. To accomplish this, a PVCcap is formed which is inserted into the end of the pipe at theunderground structure. This cap is held in the pipe with an expansionring, and the cap extends out of the pipe end and is bonded to the linerand to a fiberglass disc which is attached to the bottom of theunderground structure.

The liner of the present invention and the pipe seal together completelyprotect the original underground structure walls from any furthercontact with acid products from within the underground structure whilealso strengthening the walls and preventing ground water from leakinginto the underground structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified cross section view of an underground structurewith the liner of the preferred embodiment installed in the interior ofthe underground structure.

FIG. 2 is an enlarged cross section view of a portion of the liner ofthe preferred embodiment of the invention.

FIG. 3 is a simplified cross section of a seam used to attach the bottomof the liner to the wall and to attach flat side panels to each other toform the wall and the bottom of the liner.

FIG. 4 is a simplified cross section view of the preferred embodiment ofa seal between the liner of the invention and a pipe entering theunderground structure.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a simplified cross section view of underground structure 10with liner 12 of the preferred embodiment installed in the interior ofunderground structure 10. Underground structure 10 has vertical walls 14and bottom slab 16, and although underground structure 10 is shown inFIG. 1 as constructed of concrete, older underground structures aresometimes constructed of bricks or concrete blocks. Liner 12 isinstalled to seal cracks within underground structure walls 14 and toreinforce walls 14 to prevent continuing damage.

Pipes 18 penetrate walls 14 as they do in most underground structures tomove sewage or to give access to other utilities, and pipes 18 must alsobe sealed to liner 12. The description of this seal follows with thediscussion of FIG. 4.

FIG. 2 is an enlarged cross section view of a portion of liner 12 of thepreferred embodiment of the invention when it is attached to undergroundstructure wall 14.

Liner 12 of the present invention includes two essential layers.Interior layer 20, which is exposed to the interior environment ofunderground structure 10, is an acid resistant layer. The second layeris fleece layer 22, a continuous layer of fibers protruding from acidresistant interior layer 20. Fleece layer 22 is integrated into acidresistant interior layer 20 and is impregnated with an epoxy resin whichit captures and retains. When fleece layer 22 is in contact withunderground structure wall 14, the fibers of fleece layer 22 function asmultiple anchors as they contact underground structure wall 14 and forma continuous layer which conforms to irregularities and crevices in theunderground structure wall surface.

In the preferred embodiment the material of the acid resistant layer is0.018 inch thick polyvinyl chloride (PVC), thermally bonded to a 10 oz.polyester fleece layer. The product is manufactured by FerlandIndustries. A liner made to this specification will resist acids such assulfuric acid. The thicknesses of all of these layers can be adjustedfor the specific application to yield, for instance, greater strengthand superior acid resistance.

Several methods of applying the epoxy resin are available. A two partresin can be applied to fleece layer 22 or to the fiberglass layer 24(FIG. 3) at the installation site just before insertion into undergroundstructure 10. The resin used for the preferred embodiment is a mixtureof 60% part A and 40% part B, with part A being 90% PEP 6128 and 10% PEP6748 and part B being 30% PEP 9140 and 70% PEP 9254. All the PEPproducts are sold by Pacific Epoxy Polymers, Inc. of Richmond, Mo.

A delayed reaction epoxy can also be applied to liner 12 before itarrives at the installation site, in which case the epoxy is cured bysubjecting the assembly to elevated temperature or to some otheractivating agent such as light or other radiation.

FIG. 3 is a simplified cross section of seam 26 which is used to attachbottom panel 28 of liner 12. The same seam 26 is used to attachindividual flat side panels to each other to form walls 14 or bottompanel 28 of liner 12. The seam between flat side panels can be betterunderstood if bottom panel 28 of FIG. 3 and panel 12′, shown in phantomlines, are visualized as adjacent side panels viewed from the top. Allof seams 26 are formed by bonding together impervious layers 20 and 30of adjacent panels. Such bonds are made by conventional methods such asby the use of fusion welding of the materials, by sewing, or by the useof an intermediate bonding material such as epoxy or glue. Suchmaterials are available on the market as HH-66 PVC glue sold by R-HProducts Co. Inc. of Acton, Mass.

It is important that seam 26 he formed by joining together imperviousinterior layers 20 and 30 as opposed to the more traditional techniqueof simply overlaying adjacent panels. Overlaying the adjacent panelsattaches an impervious layer to a fleece layer 22, and although thejoint would probably be structurally sound, there is little assurancethat it would be leak tight.

The use of seams 26 to form an entirely enclosed liner 12 provides anadded benefit over the prior art. Existing underground structure linershave all been installed by the use of a separate removable air tightbladder which is placed within the liner when the liner is inserted intothe underground structure. The separate bladder is then inflated to holdthe liner against the underground structure wall as the epoxy resincures and the bladder is removed after curing.

Seams 26 and bottom 28 produce a liner which is itself completely leaktight, and it therefore does not require the use of an inflationbladder. A liner such as liner 12 is directly inflated in the samemanner as previous bladders, with hot air or a mixture of air and steam,but does not require the cost, time, and extra labor of installing theadditional inflatable bladder.

As also shown in FIG. 3, reinforcing material can also be added on topof or within fleece layer 22. Typically this reinforcing material iscloth layer 24 which is also saturated with resin, and it can be addedto the outside of fleece layer 22. However, the reinforcing material canalso be integrated into the epoxy resin by spraying a mixture of epoxyresin and fibers directly onto the fleece layer. The cloth layer of thepreferred embodiment is 18 or 24 oz. fiberglass cloth sold by VetrotexAmerica of Wichita Falls, TX.

FIG. 4 is a simplified cross section view of the preferred embodiment ofa seal between underground structure liner 12 and pipe 18 enteringunderground structure 10. When properly prepared, such a seal can bemade after liner 12 has been inflated and attached to undergroundstructure wall 14. In preparation for the seal, capping strip 32 isplaced into pipe 18 and held tightly in place with conventionalexpansion ring 34. Capping strip is then expanded and bonded tounderground structure wall 14 at end 36, and also bonded at edge 38 tofiberglass leveling disc 40. Temporary plywood disc 42 is then setagainst the end of pipe 18 to prevent liner 12 from expanding into pipe18. Later, after liner 12 is bonded to underground structure wall 14 andto fiberglass disc 40, temporary plywood disk 42 and the portion ofliner 12 bonded to it are removed to open up pipe 18 again.

The present invention thereby furnishes a underground structure linerwith improved bonding to the underground structure wall and alsoeliminates the need for an additional inflation bladder.

It is to be understood that the form of this invention as shown ismerely a preferred embodiment. Various changes may be made in thefunction and arrangement of parts; equivalent means may be substitutedfor those illustrated and described; and certain features may be usedindependently from others without departing from the spirit and scope ofthe invention as defined in the following claims.

1. A method of repairing a manhole, comprising the steps of: providing aliner that substantially conforms to the shape of said manhole whereinsaid manhole comprises an entrance, at least one wall, and a floor,wherein said floor is substantially parallel to said entrance, and saidliner comprises a first layer consisting of an impermeable acidresistant material with first and second opposing surfaces and a secondlayer comprising fibers that are integrated into said second surface ofsaid first layer of said impermeable acid resistant material; providingan inflatable bladder in combination with said liner wherein saidbladder is in direct contact with said first surface of said first layerof said impermeable acid resistant material; applying epoxy resin tosaid second layer; lowering said liner, in combination with saidinflatable bladder, into said manhole; inflating said bladder until saidbladder conforms to said wall and said floor; curing said epoxy resin;and removing said bladder from said manhole leaving said first surfaceof said first layer of said impermeable acid resistant material exposedto the interior environment of said manhole.
 2. The method of claim 1wherein said liner further includes a reinforcing material in contactwith said second layer.
 3. The method of claim 2 wherein saidreinforcing material is fiberglass.
 4. The method of claim 1 whereinsaid impermeable acid resistant material is polyvinyl chloride.
 5. Themethod of claim 1 wherein said second layer is a layer of fleece.
 6. Themethod of claim 5 wherein said fleece is made of polyester.
 7. Themethod of claim 1 wherein said epoxy resin is a two part epoxy resin. 8.The method of claim 1 wherein said epoxy resin is a delayed reactionepoxy resin.